D-Money

Handling amounts of money safely and efficiently.

Floating point is imprecise. Integer is fragile. BigNum and similar are slow. All lack type safety, like forbidding addition different currencies.

Features:

support different rounding modes
can not mix currencies (e.g. EUR vs USD)
efficient integer arithmetic
overflow checking for arithmetic
type checking for currencies, precision, and rounding mode
yet generic equality and comparison

    alias EUR = currency!("EUR");

    assert(EUR(100.0001) == EUR(100.00009));
    assert(EUR(3.10) + EUR(1.40) == EUR(4.50));
    assert(EUR(3.10) - EUR(1.40) == EUR(1.70));
    assert(EUR(10.01) * 1.1 == EUR(11.011));

    writefln("%d", EUR(3.6)); // "4EUR"
    writefln("%f", EUR(3.141592)); // "3.1416EUR"
    writefln("%.2f", EUR(3.145)); // "3.15EUR"
    writefln("%.2f", EUR("3.145")); // "3.15EUR"

Scope is smaller than JSR 354, for example, which also considers conversion and meta data. A conversion rate depends on target date and time, the currencies involved, the provider, the amount, and other factors. If you need meta data, then wrap currency into your own data type.

Available via dub on code.dlang.org.

Licence is Boost v1.0.